Author
Henrik Møller (1998)

Trends in sex-ratio, testicular cancer and male reproductive hazards: Are they connected?

A number of reports have appeared in the literature in recent years documenting a decline is the number of male births and thus sex ratio (%male births). However, there is little known concerning the factors that influence sex ratio or the mechanism involved. This paper is the first to articulate the idea that changes in sex ratio seen in live births in a variety of western nations may be associated with the observed increase in testicular cancer and with the purported decline in semen quality also observed in many industrialized regions. Moller cites several papers that identified a population-wide decline in sex ratio (% male births) over recent decades and compares these with historic annual sex ratio data for the 4 Scandinavian nations dating back to as early as 1750 for Sweden. These data suggest that recent sex ratio trends indicate a reduction from an all time peak in male/female ratio that occurred in these nations immediately after the Second World War with a consistent decline after the war. In addition, Moller cites that observed increases in testicular cancer have occurred during the same historic period as the recent decline in sex ratio. Although there appears to be a correlation in the timing of these events the degree of change does not match well as the nation with the least increase in testis cancer (Finland) demonstrates by far the most dramatic decline in national sex ratio at birth. If these two population characteristics were causally linked one would expect a closer agreement between the two in terms of the degree of change.

Moller goes on to suggest that these population-based observations may be causally associated and presents novel epidemiological data to support this hypothesis. He shows case control data demonstrating that the ratio of male to female infants fathered prior to diagnosis of testis cancer (47%) was lower than the average sex ratio for the population as a whole (51.4%). To support the contention that this is further related to poor fertility, data is presented showing that the number of children fathered by men prior to a diagnosis of testicular cancer was lower than control men of comparable age. The author concludes that this evidence provides support for the hypothesis that human male reproductive health is declining due to some poorly characterized hazard. This decline in male health is indicated by an increase in a common syndrome comprising declining semen quality, increased risk of testis cancer and, possibly, increased genital malformations although no evidence was presented to support the inclusion of the latter factor. Although no specific hazards are suggested, Moller does cite examples of dioxin and dichlorobromopropane exposure of men that has led to both reduced fertility and reduced sex ratio of their offspring. This paper does present an integrating hypothesis linking exposure to environmental contaminants and adverse reproductive health outcomes that should be tested through epidemiological studies.